bfd/bfdwin.c

   1 /* Support for memory-mapped windows into a BFD.
   2    Copyright 1995, 1996, 2001, 2002, 2003 Free Software Foundation, Inc.
   3    Written by Cygnus Support.
   4
   5 This file is part of BFD, the Binary File Descriptor library.
   6
   7 This program is free software; you can redistribute it and/or modify
   8 it under the terms of the GNU General Public License as published by
   9 the Free Software Foundation; either version 2 of the License, or
  10 (at your option) any later version.
  11
  12 This program is distributed in the hope that it will be useful,
  13 but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 GNU General Public License for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with this program; if not, write to the Free Software
  19 Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA.  */
  20
  21 #include "sysdep.h"
  22
  23 #include "bfd.h"
  24 #include "libbfd.h"
  25
  26 /* Currently, if USE_MMAP is undefined, none if the window stuff is
  27    used.  Okay, so it's mis-named.  At least the command-line option
  28    "--without-mmap" is more obvious than "--without-windows" or some
  29    such.  */
  30
  31 #ifdef USE_MMAP
  32
  33 #undef HAVE_MPROTECT /* code's not tested yet */
  34
  35 #if HAVE_MMAP || HAVE_MPROTECT || HAVE_MADVISE
  36 #include <sys/mman.h>
  37 #endif
  38
  39 #ifndef MAP_FILE
  40 #define MAP_FILE 0
  41 #endif
  42
  43 static int debug_windows;
  44
  45 /* The idea behind the next and refcount fields is that one mapped
  46    region can suffice for multiple read-only windows or multiple
  47    non-overlapping read-write windows.  It's not implemented yet
  48    though.  */
  49
  50 /*
  51 INTERNAL_DEFINITION
  52
  53 .struct _bfd_window_internal {
  54 .  struct _bfd_window_internal *next;
  55 .  void *data;
  56 .  bfd_size_type size;
  57 .  int refcount : 31;           {* should be enough...  *}
  58 .  unsigned mapped : 1;         {* 1 = mmap, 0 = malloc *}
  59 .};
  60 */
  61
  62 void
  63 bfd_init_window (bfd_window *windowp)
  64 {
  65   windowp->data = 0;
  66   windowp->i = 0;
  67   windowp->size = 0;
  68 }
  69
  70 void
  71 bfd_free_window (bfd_window *windowp)
  72 {
  73   bfd_window_internal *i = windowp->i;
  74   windowp->i = 0;
  75   windowp->data = 0;
  76   if (i == 0)
  77     return;
  78   i->refcount--;
  79   if (debug_windows)
  80     fprintf (stderr, "freeing window @%p<%p,%lx,%p>\n",
  81              windowp, windowp->data, windowp->size, windowp->i);
  82   if (i->refcount != 0)
  83     return;
  84
  85   if (i->mapped)
  86     {
  87 #ifdef HAVE_MMAP
  88       munmap (i->data, i->size);
  89       goto no_free;
  90 #else
  91       abort ();
  92 #endif
  93     }
  94 #ifdef HAVE_MPROTECT
  95   mprotect (i->data, i->size, PROT_READ | PROT_WRITE);
  96 #endif
  97   free (i->data);
  98 #ifdef HAVE_MMAP
  99  no_free:
 100 #endif
 101   i->data = 0;
 102   /* There should be no more references to i at this point.  */
 103   free (i);
 104 }
 105
 106 static int ok_to_map = 1;
 107
 108 bfd_boolean
 109 bfd_get_file_window (bfd *abfd,
 110                      file_ptr offset,
 111                      bfd_size_type size,
 112                      bfd_window *windowp,
 113                      bfd_boolean writable)
 114 {
 115   static size_t pagesize;
 116   bfd_window_internal *i = windowp->i;
 117   bfd_size_type size_to_alloc = size;
 118
 119   if (debug_windows)
 120     fprintf (stderr, "bfd_get_file_window (%p, %6ld, %6ld, %p<%p,%lx,%p>, %d)",
 121              abfd, (long) offset, (long) size,
 122              windowp, windowp->data, (unsigned long) windowp->size,
 123              windowp->i, writable);
 124
 125   /* Make sure we know the page size, so we can be friendly to mmap.  */
 126   if (pagesize == 0)
 127     pagesize = getpagesize ();
 128   if (pagesize == 0)
 129     abort ();
 130
 131   if (i == 0)
 132     {
 133       i = bfd_zmalloc (sizeof (bfd_window_internal));
 134       windowp->i = i;
 135       if (i == 0)
 136         return FALSE;
 137       i->data = 0;
 138     }
 139 #ifdef HAVE_MMAP
 140   if (ok_to_map
 141       && (i->data == 0 || i->mapped == 1)
 142       && (abfd->flags & BFD_IN_MEMORY) == 0)
 143     {
 144       file_ptr file_offset, offset2;
 145       size_t real_size;
 146       int fd;
 147       FILE *f;
 148
 149       /* Find the real file and the real offset into it.  */
 150       while (abfd->my_archive != NULL)
 151         {
 152           offset += abfd->origin;
 153           abfd = abfd->my_archive;
 154         }
 155       f = bfd_cache_lookup (abfd);
 156       if (f == NULL)
 157         return FALSE;
 158       fd = fileno (f);
 159
 160       /* Compute offsets and size for mmap and for the user's data.  */
 161       offset2 = offset % pagesize;
 162       if (offset2 < 0)
 163         abort ();
 164       file_offset = offset - offset2;
 165       real_size = offset + size - file_offset;
 166       real_size = real_size + pagesize - 1;
 167       real_size -= real_size % pagesize;
 168
 169       /* If we're re-using a memory region, make sure it's big enough.  */
 170       if (i->data && i->size < size)
 171         {
 172           munmap (i->data, i->size);
 173           i->data = 0;
 174         }
 175       i->data = mmap (i->data, real_size,
 176                       writable ? PROT_WRITE | PROT_READ : PROT_READ,
 177                       (writable
 178                        ? MAP_FILE | MAP_PRIVATE
 179                        : MAP_FILE | MAP_SHARED),
 180                       fd, file_offset);
 181       if (i->data == (void *) -1)
 182         {
 183           /* An error happened.  Report it, or try using malloc, or
 184              something.  */
 185           bfd_set_error (bfd_error_system_call);
 186           i->data = 0;
 187           windowp->data = 0;
 188           if (debug_windows)
 189             fprintf (stderr, "\t\tmmap failed!\n");
 190           return FALSE;
 191         }
 192       if (debug_windows)
 193         fprintf (stderr, "\n\tmapped %ld at %p, offset is %ld\n",
 194                  (long) real_size, i->data, (long) offset2);
 195       i->size = real_size;
 196       windowp->data = (bfd_byte *) i->data + offset2;
 197       windowp->size = size;
 198       i->mapped = 1;
 199       return TRUE;
 200     }
 201   else if (debug_windows)
 202     {
 203       if (ok_to_map)
 204         fprintf (stderr, _("not mapping: data=%lx mapped=%d\n"),
 205                  (unsigned long) i->data, (int) i->mapped);
 206       else
 207         fprintf (stderr, _("not mapping: env var not set\n"));
 208     }
 209 #else
 210   ok_to_map = 0;
 211 #endif
 212
 213 #ifdef HAVE_MPROTECT
 214   if (!writable)
 215     {
 216       size_to_alloc += pagesize - 1;
 217       size_to_alloc -= size_to_alloc % pagesize;
 218     }
 219 #endif
 220   if (debug_windows)
 221     fprintf (stderr, "\n\t%s(%6ld)",
 222              i->data ? "realloc" : " malloc", (long) size_to_alloc);
 223   i->data = bfd_realloc (i->data, size_to_alloc);
 224   if (debug_windows)
 225     fprintf (stderr, "\t-> %p\n", i->data);
 226   i->refcount = 1;
 227   if (i->data == NULL)
 228     {
 229       if (size_to_alloc == 0)
 230         return TRUE;
 231       return FALSE;
 232     }
 233   if (bfd_seek (abfd, offset, SEEK_SET) != 0)
 234     return FALSE;
 235   i->size = bfd_bread (i->data, size, abfd);
 236   if (i->size != size)
 237     return FALSE;
 238   i->mapped = 0;
 239 #ifdef HAVE_MPROTECT
 240   if (!writable)
 241     {
 242       if (debug_windows)
 243         fprintf (stderr, "\tmprotect (%p, %ld, PROT_READ)\n", i->data,
 244                  (long) i->size);
 245       mprotect (i->data, i->size, PROT_READ);
 246     }
 247 #endif
 248   windowp->data = i->data;
 249   windowp->size = i->size;
 250   return TRUE;
 251 }
 252
 253 #endif /* USE_MMAP */